Resolved Urgent problem - Exporting from virtuemart

Hi Weve had export templates that have been exporting orders for 10+ years. but suddenly last night they are failing.
its a front end cron executed like this...

https://www.xxxxxxx.co.uk/index.php?option=com_csvi&view=export&csvi_template_id=68&exportto=todownload&key=xxxxx&task=export&tmpl=component&form.orderlist=863645,863644,863640,863638,863636,863635,863633,863631,863630,863628,863568,863484,863446


and all of a sudden its redirectign to the front end of the website with a message Error: COM_CSVI_EXPORT_RUN_FAILED

Any suggestions

Oh were still on J3.10.12 and vm 3.8 (yes I know)